During Endoscopic surgical procedures, a surgical site such as a knee joint, shoulder joint or other cavity in the body of a human or animal is viewed with an endoscope. Further in this document, the surgical site for an Endoscopic procedure is referred to as the body cavity. The body cavity is irrigated with a clear liquid in order to expand it, improve the view of it and to rinse the cavity. The irrigation is achieved by means of a pump. This pump is further in this document referred to as an inflow liquid pump. The clear liquid is as a rule saline, and the pump is usually a peristaltic roller type pump. Also, the surgical procedures normally involve the removal of, or work on tissue, for instance the meniscus of the knee. This results in debris, namely particles of various sizes of tissue floating around in the liquid in the body cavity. These particles are routinely removed by rinsing. To rinse out blood and/or debris, the liquid in the body cavity is replaced by introducing or increasing liquid flow through the body cavity. The outflow of the irrigation liquid is normally transported via a tubing to a waste bucket.
Existing liquid management systems are either operated by a fixed flushing flow selected by the operator of the system when starting the procedure, or by a fixed pressure target for the system.
Cassettes for peristaltic pumps and similar medical applications have been developed in order to create and improve the handling of the tubing and flow of liquid. EP0362822 B1 “Disposable vacuum/peristaltic pump cassette system” describes a disposable cassette and U.S. Pat. No. 6,962,488 B2 “Surgical cassette having an aspiration pressure sensor” discloses a cassette system used for eye surgery and design with channels for the fluid based on hard and soft plastic.
Detection of blood and debris in outflow tubing is previously discussed in WO 2007/114776 “Method and device for irrigation of body cavities” disclosing a method and apparatus for detecting biological material such as blood and debris in an irrigation fluid from a body cavity. The outflow liquid device detecting biological material consists of light emitting diodes (LED) and optical sensors for hemoglobin, debris and optionally a calibrating detector mounted on the tubing. The described optical detector is fitted on the housing for the pump system, but may optionally be fitted near or even directly by or within the surgical instrumentation that is forming the liquid path emerging from the patient, such as a shaver tool or cannula. The described optical light emitting and sensor arrangement forms an optical path in the liquid in the housing of a vessel in the liquid outflow path of the irrigation fluid.
The detection of particles and methods to analyze fluids such as body fluids are is well known within the area of dialysis. WO2007044548 “fluid handling system” discusses a cassette system for analyzing body fluids for determining the concentration of analyte in a sample. A patient cassette system with functions such as sensors for hemoglobin and optical or ultrasonic “bubble sensors” indicate the presence of air in the liquid pathway. Furthermore, since it is crucial not to infuse air into blood systems, methods are used to indicate air bubbles connected to a warning system. U.S. Pat. No. 6,511,454 B1 “irrigation/aspiration apparatus and irrigation/aspiration cassette” discloses such a system. And EP319278B1 “Disposable cassette for a medication infusion system” teaches a design for removal of air bubbles.
While existing products for dialysis and medical liquid inflow systems may be suitable for the particular purpose to which they address, they are not as suitable for optical measurement of diluted particles in for example aspirated fluid.
Optical measurement of particles such as body fluids in a sample in a liquid such as irrigation fluid is highly dependent on the housing of the sample volume and the implementation of the measurement system. The optical path needs to be long enough in order to detect low numbers of particles. Noise from for example air bubbles and unnecessary differences in optical refraction along the optical path should be avoided and the housing of the sample volume should be stable and easily mounted to the optical sensors. The wording “sample volume” refers to, and will hereinafter be referred to, the liquid in the optical path in the liquid in the housing.
In these respects, the detection of particles and design of housing of the sample volume according to the present invention substantially departs from the conventional concepts and designs of the prior art, and in doing so provides products primarily developed for the purpose of an improved measurement of particles such as blood and debris in a sample volume such as that in a cassette system for aspirated irrigation fluid.